1. Field of the Invention
The present invention relates to a novel polymeric liquid-crystal compound having an optically active group on its polymer side chain, a polymeric liquid-crystal composition comprising the polymeric liquid-crystal compound, and a polymeric liquid-crystal device using these.
The polymeric liquid-crystal compound of the present invention and the polymeric liquid-crystal composition containing the polymeric liquid-crystal compound can be used as materials for optoelectronics or materials for optical devices as typified by display devices and memories.
2. Related Background Art
Hitherto known liquid-crystal devices include a device that employs the twisted nematic liquid crystal as disclosed in M. Schadt and W. Helfrich, Voltage Dependent Optical Activity of a Twisted Nematic Liquid Crystal, "Applied Physics Letters", Vol. 18, No. 4, pp. 127-128 (Feb. 15, 1971). This twisted nematic liquid crystal, however, has a problem of crosstalk occurring at the time of a time division drive using a matrix electrode system having a high density of picture elements, and hence has a restriction in the number of the picture elements.
There has been also a limit in its use as a display device because of a slow electric field response and poor visual-field angle characteristics. This liquid crystal has another problem that a very complicated process is required for the formation of a thin-film transistor for each picture element and moreover a display device with a large area can be produced with difficulty.
For eliminating the disadvantages of such a conventional liquid-crystal device, Clark and Lagerwall have proposed to use a liquid-crystal device comprised of a bistable element (see Japanese Patent Appln. Laid-Open No. 56-107216 and U.S. Pat. No. 4,367,924).
Commonly used as this liquid crystal comprised of a bistable element is a ferroelectric liquid crystal comprised of a chiral smectic C phase (Sm*C) or H phase (Sm*H). This ferroelectric liquid crystal exhibits spontaneous polarization, and hence has a very quick response and moreover can produce a bistable state with memory performance. In addition, it has superior visual-field angle characteristics, and hence can be considered to be suited as a material for display with a large capacity and a large area. When, however, a liquid crystal cell is actually formed, it is difficult to achieve a monodomain over a large area, and a technical problem has remained unsettled in making a display device with a large screen.
It is also known to use a polymeric liquid-crystal as a memory medium.
This can be exemplified by the heat-writing memory as disclosed in V. Shibaev, S. Kostromin, N. Plate, S. Ivanov, V. Vestrov and I. Yakovlev, Thermotropic Liquid Crystalline Polymers 14, "Polymer Communications", Vol. 24, pp. 364-365.
This method, however, can attain only a poor contrast since scattering of light is utilized for reading, and also has the problem that the response speed is much lower than low molecular liquid crystal because of high viscosity of polymer. Accordingly, this method has not been put into practical use.
Japanese Patent Appln. Laid-Open No. 63-72784, No. 63-99204 and No. 63-161005 disclose ferroelectric polymeric liquid-crystals having as a chiral moiety a hydrocarbon alcohol such as amyl alcohol. These, however, all have the disadvantages such that they exhibit too small spontaneous polarization because of their structure to give a quick response.